Dementia in Germany: Epidemiology and Prevention Potential
Background: The further development of public-health approaches for the prevention of dementia requires estimates of the number of people with dementia, trends in incidence and prevalence, and the potential impact of preventive measures.
Methods: The projections described here are based on incidence and prevalence data for Europe and on current and projected population figures from the German Federal Statistical Office. Four scenarios were calculated on the basis of two different population projections and the assumption of either stable or declining prevalence. Data from the German Aging Survey were used to estimate the prevention potential for eleven potentially modifiable risk factors for dementia. Weighting factors were determined to adjust for correlations between risk factors.
Results: Approximately 1.8 million people were living with dementia in Germany as of December 31, 2021; the number of new dementia cases in 2021 is estimated at 360 000 to 440 000. In 2033, depending on the scenario, 1.65 to 2 million people aged 65 and older may be affected; we consider likelihood of the lower end of this range to be very low. It is estimated that 38% of these cases are associated with 11 potentially modifiable risk factors. A 15% reduction in the prevalence of risk factors could potentially decrease the number of cases by up to 138 000 in 2033.
Conclusion: We assume that the number of people with dementia in Germany will increase, but there is considerable prevention potential. Multimodal prevention approaches to promote healthy aging should be further developed and put into practice. Better data are needed on incidence and prevalence of dementia in Germany.
Ensuring optimal care and social participation for people living with dementia places high demands on the healthcare system and society in general (1, 2). The epidemiologic study of dementia enables us to determine how many people in Germany need this support now and how many will need it in the future. The first aim of this paper is to provide an updated estimate of the number of people with dementia in Germany, the number of new cases per year, and projected case numbers for 2033.
The international working group GBD 2019 Dementia Forecasting Collaborators has predicted rising case numbers of dementia around the world. A threefold rise in the number of people with dementia is projected for the next three decades, from an estimated 57.4 million in 2019 to 152.8 million in 2050 (3). On the other hand, there are already initial studies from Western countries reporting a decline in the incidence and prevalence of dementia (4, 5), which is attributed, in turn, to a lowering of dementia risk factors in the population (e.g., the broadening of educational opportunities and the adoption of healthier lifestyles) (4, 6). The lifestyle factors that are known to promote dementia are a promising starting point for preventive measures. The WHO also emphasizes the important role of prevention in its guideline on dementia risk reduction (7).
The Lancet Commission recently summarized the evidence concerning twelve potentially modifiable risk factors for dementia (8, 9): a low educational level in early life, hearing loss, traumatic brain injury, hypertension, excessive alcohol consumption, and obesity in middle age, as well as smoking, depression, social isolation, physical inactivity, air pollution, and diabetes in old age. The Lancet Commission estimated that two-fifths of dementia cases worldwide may be attributable to these factors, of which hearing loss, low educational level, and smoking are the most important (8).
Prevention measures that address multiple lifestyle factors at once are especially promising (10). One of the larger multimodal prevention trials, the FINGER trial from Finland (11), concerned older people at increased risk for dementia. The authors reported small but significant positive effects on general cognition, compared to a control group, in an intervention group receiving two years of dietary counseling, physical and cognitive training, and physician feedback on cardiovascular risk factors. This reported benefit is encouraging in view of the major challenges facing dementia prevention trials: the slow development of the condition over decades makes it difficult to identify appropriate target groups and time points for intervention (10, 12). Prevention measures are now undergoing further development in an international dementia prevention network (10), in which Germany is also participating (13).
The latest projection of the potential for dementia prevention in German was made in 2016 (14). Since then, evidence has arisen for further potentially modifiable risk factors. Knowledge of the main risk factors and prevention potential in Germany is important for the further development of preventive approaches in this country. The second aim of this paper is, therefore, to give an updated projection of the prevention potential.
The number of people with dementia
The estimated number of people with dementia in Germany in 2021 is derived from the age- and sex-specific prevalences for Europe contained in the WHO Global Status Report (15), combined with updated population figures from the Federal Statistical Office as of December 31, 2021 (16).
New cases per year
The age-specific incidence rates for Western Europe contained in the World Alzheimer Report (17) and the updated population figures from the Federal Statistical Office as of December 31, 2021 (16) were used to estimate the number of new cases in 2021. This method may overestimate the number of new cases, as it exclusively concerns the age group in question without taking pre-existing disease into account. A further estimate was calculated with a correction for prevalent cases, by means of age-specific prevalences from the WHO Global Status Report (15) and the population status as of December 31, 2020 (18). This, however, might underestimate the true incidence, because, among other reasons, the survival rate of people suffering from dementia in the individual age groups is not known.
Projected trends in case numbers up to 2033
Future trends in dementia case numbers will depend on changes in life expectancy, the age structure of the population, and the prevalence of dementia. Population data for 2033 were taken from the 15th coordinated population projection of the Federal Statistical Office as of December 31, 2021 (19). Two population variants were used: relatively young population (small increase in life expectancy to 82.6 [boys] and 86.1 years [girls] by 2070; high increase in fertility rate to 1.67 children per woman from 2032 onward, with a final figure of 1.7; decline in annual net immigration from 1.5 million in 2022 to 350 000 in 2033) and relatively old population (marked increase in life expectancy to 86.4 years [boys] and 90.1 years [girls] by 2070; decline in fertility to 1.44 children per woman by 2032, constant thereafter; decline in annual net immigration from 1.1 million in 2022 to 150 000 in 2033).
Age- and sex-specific prevalence figures for Europe were taken from the WHO Global Status Report (15). The case numbers for 2033 were estimated on the basis of stable dementia prevalences and, alternatively, for dementia prevalences that declined by 1.2% per year in all age and sex groups. A study based on health insurance data had revealed a relative mean decline in dementia prevalence of 1.2% per year for Germany between 2009 and 2012 (5).
Calculations were made for four scenarios:
- relatively old population and stable prevalence
- relatively young population and stable prevalence
- relatively old population and decreasing prevalence
- relatively young population and decreasing prevalence.
Prevention potential was calculated in a manner analogous to that used by the Lancet Commission (8, 9). Adjusted population attributable fractions (PAFs) were calculated for eleven potentially modifiable risk factors: low educational level, hearing loss, hypertension, excessive alcohol consumption, obesity, smoking, depression, social isolation, physical inactivity, air pollution, and diabetes.
A PAF, on the assumption of a causal relationship, indicates the fraction of disease cases in a population that can be attributed to a particular risk factor. Because multiple risk factors for dementia were considered, a modified version of Levin‘s formula was used (20) incorporating the prevalences of the risk factors, the relative risks, and weighting factors to adjust for the simultaneous presence of multiple risk factors (e.g., diabetes, obesity, and hypertension) (20). The relative risks were taken from a recent Lancet Commission review (8); the prevalences and weighting factors were calculated on the basis of the 2017 German Aging Survey (Deutscher Alterssurvey, DEAS) published by the FDZ-DZA of the German Center for Gerontology (Deutsches Zentrum für Altersfragen, DZA) (21). Eleven of the twelve dementia risk factors were assessed in the survey—all but traumatic brain injury, for which a uniform definition and representative data are still lacking (8, 22).
In the next step, adjusted potential impact fractions (PIF) were calculated. A PIF represents the change in the fraction of disease cases ensuing from a change in the prevalence of the risk factor in the population. PIFs were calculated for 15% and 30% reductions in the prevalence of each risk factor. A more detailed description of the statistical analyses is provided in the eMethods section and in the eTable.
Number of people with dementia
The prevalence of dementia in Europe, stratified by age group and sex (15), and the estimated number of people with dementia in Germany as of Dec. 31, 2021 are shown in Table 1. As of that date, there were an estimated 1 798 000 people with dementia in Germany overall, of whom 1 696 000 were aged 65 and older. About two-thirds of those affected were women.
New cases per year
In 2021, according to our estimate, between 360 000 and 440 000 people aged 65 and older were newly affected by dementia.
Projected trends in case numbers up to 2033
The case rates of dementia in 2033, predicted in each of four scenarios, are shown in Table 2. On the assumption that the prevalence of dementia remains stable, the number of people in Germany aged 65 and older who will be living with dementia in 2033 is predicted to lie in the range of 1.91 million (scenario 2) to 2 million people (scenario 1). On the other hand, if the prevalence of dementia drops by 1.2% each year until 2023, the corresponding figures are 1.65 million (scenario 4) to 1.74 million people (scenario 3).
The prevalences, relative risks, commonalities, and adjusted PAFs and PIFs for eleven of the twelve modifiable risk factors for dementia selected by the Lancet Commission are shown in Table 3. Our calculations yield a prevention potential of 38%: i.e., on the assumption of a causal relationship, more than one in three cases of dementia can be attributed to the risk factors that were considered. Most cases of dementia in Germany are associated with the risk factors hearing loss (6.3%), hypertension (6.1%), depression (4.7%), obesity (4.6%), and smoking (4.0%).
The Figure depicts the number of cases of dementia in Germany in 2033 (basis: 2 million affected persons, as in scenario 1) that could theoretically be avoided if the population-based prevalence of the risk factors were reduced by 15% or even 30%. A 15% reduction could reduce the number of people affected by up to 138 000 in 2033, and a 30% reduction could reduce it by up to 265 000.
Dementia remains a major public health problem, with approximately 1.8 million affected people in Germany as of the end of 2021, of whom an estimated 360 000 to 440 000 were newly affected in that calendar year. By 2033, there may be as many as 2 million affected people aged 65 and over. They will need custodial care, nursing, therapy and rehabilitation services, as well as expanded opportunities for social participation and for relief and support services. Many such measures are already part of the National Dementia Strategy (1) and must now be implemented step by step.
Future trends in dementia case numbers will depend on a variety of factors (23, 24). Decreasing prevalences and incidences have recently been reported in some Western countries (4) and are thought to be due to the decreasing prevalence of risk factors for dementia (4, 6). If this trend continues, the number of people with dementia in 2033 could be lower, with approximately 1.7 million affected persons aged 65 years and over. Experts warn, however, that the observed decline may yet be reversed by an increase in risk factors such as obesity, diabetes, and hypertension (6, 8, 23). Several factors—such as a reduction in the prevalence of risk factors leading to decreased dementia incidence, an increase with rising dementia incidence, or potential neuropsychiatric effects of the Covid-19 pandemic (25)—could influence the future development of case numbers (25).
Our calculations imply that more than one in three cases of dementia in Germany is associated with the eleven potentially modifiable risk factors considered here. For comparison, an estimated 7% of dementia cases are associated with the most important genetic risk factor, the ApoE є4 allele (26). The potentially modifiable risk factors considered in this study were selected on the basis of systematic reviews and expert judgment (7, 8, 9). Observational studies in which subjects were followed for decades have revealed an association of these factors with cognitive decline and dementia. The mediating mechanisms are thought to involve less cognitive reserve (e.g., through lack of education or physical activity) along with neuropathological changes (induced by, e.g., alcohol consumption, smoking, and hypertension) (7, 8). Doubts remain, however, about the causal nature of the association of dementia with depression, social isolation, and hearing loss; for these three factors, reverse causality also seems plausible, with hearing loss possibly being a symptom of the prodromal phase of dementia (27) and depression and social withdrawal possible consequences of impaired cognition (9, 28). If this is the case, the calculated prevention potential may be an overestimate. More research is needed in this area.
In the USA, the National Alzheimer Project Act Advisory Council has set a target of a 15% reduction in population-based prevalences of known modifiable risk factors (29). If this goal could be achieved in Germany in the coming few years, some 138 000 of the up to 2 million dementia cases in 2033 might theoretically be delayed or prevented. These figures make it clear that a greater effort to prevent dementia would be worthwhile, and, if successful, would lessen the burden of disease. A reduction in the prevalence of risk factors would have beneficial diseases on other diseases as well, e.g., myocardial infarction or stroke, which are largely due to the same risk factors as dementia (10).
The extent to which the prevalence of risk factors at the population level can be reduced by specific measures depends on multiple factors: the efficacy of each preventive measure, the fraction of the target population reached by it, and the fraction of those reached who actually change their behavior (30). The case of smoking shows that the prevalence of at least some risk factors can be markedly reduced: comprehensive public health measures (e.g., tax increases, non-smoker protection laws) lessened the prevalence of smoking in Germany by approximately 30% from 2003 to 2015 (31). If the risk factors for dementia in the population could be lowered by 30%, the number of cases of dementia could theoretically be reduced by as much as 265 000 by 2033.
The prevention potential that we have calculated for Germany is of a similar order of magnitude to the Lancet Commission‘s global calculations (8), yet different populations will differ in the prevalences of the individual risk factors. In Germany, fewer cases of dementia are attributable to lower levels of education because of the high educational level of the population at large. Instead, the metabolic syndrome plays a greater role, with a relatively high number of cases being attributable to hypertension and obesity. Local risk constellations should be considered in the further development of preventive approaches in Germany (and elsewhere). Moreover, the ability of evidence-based prevention approaches to yield a benefit for as many people as possible, by lowering dementia case numbers as much as possible, will depend on their rapid, comprehensive, and sustainable translation from theory into practice.
These findings must be interpreted with the limitations of the extrapolation method borne in mind. Representative data on prevalence and incidence at the population level are still lacking. Germany does not have a nationwide dementia registry, unlike France, Sweden, or South Korea (32). The prevalence and incidence figures employed here are derived from European studies, some of which are older, and were reported for broad age categories. Data on prevalence are variable, particularly for younger patients (15, 33). Moreover, the reported case numbers are likely to be underestimates, as dementia is substantially underdiagnosed (34, 35).
Levin’s formula can be used to estimate the prevention potential from reducing a single risk factor, considered in isolation. Because this overestimates the prevention potential from reducing multiple risk factors, we used a modified version of the formula, with weighting factors (20); yet even the modified formula does not account for possible interactions between risk factors. There remains considerable uncertainty about interactions between risk factors for dementia, whether these are modifiable or not (36). Moreover, the present study concerns the prevention potential for dementia as a whole, as the data are currently lacking that would enable us to consider the various forms of dementia separately (9).
The number of people with dementia in Germany is still rising, with major implications for the health care system and for society. At the same time, knowledge about potentially modifiable risk factors is growing. A reduction in case numbers will require the further development and rapid population-wide implementation of preventive approaches to enable healthy aging.
The data presented here regarding the number of people suffering from dementia and the number of new cases per year have already been published, in part, in an information leaflet of the German Alzheimer Society: see www.deutsche-alzheimer.de/fileadmin/Alz/pdf/factsheets/infoblatt1_haeufigkeit_demenzerkrankungen_dalzg.pdf.
Conflict of interest statement
RT is a member of the board of directors of the German Alzheimer Society (Deutsche Alzheimer Gesellschaft e. V.) The other authors state that they have no conflict of interest.
Manuscript received on 13 September 2022, revised version accepted on 5 April 2023.
Translated from the original German by Ethan Taub, M.D.
Dr. rer. nat. Iris Blotenberg
Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE)
Ellernholzstr. 1–2, D-17489 Greifswald, Germany
Cite this as:
Blotenberg I, Hoffmann W, Thyrian JR: Dementia in Germany: epidemiology and prevention potential. Dtsch Arztebl Int 2023; 120: 470–6. DOI: 10.3238/arztebl.m2023.0100
eReferences, eMethods, eTables, eFigures, eBox:
Institute for Community Medicine, Greifswald University Medicine: Prof. Dr. med. MPH Wolfgang Hoffmann, Prof. Dr. rer. med. Jochen René Thyrian
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